There is a continuous increase in the number of radio-frequency applications, such as, for example, in motor vehicle radar technology. Low costs of the devices and integrated circuits are a prerequisite for the wide spreading of applications of this type. Thus, hybrid setups having high operating and compensating complexity, as have traditionally been used in radio-frequency technology, are ruled out from being used in mass applications. However, an integration of as many radio-frequency functions as possible and a good and cheap setup technology are necessary. Depending on the frequency band and the application, the integration of the circuits is possible in different semiconductor technologies. Candidates are both silicon technologies (Si technologies) and also III-V semiconductor technologies. Frequency bands at 5.8 GHz, 10.5 GHz, 24 GHz, 48 GHz and 77 GHz are, for example, employed for anti-collision systems in motor vehicle technology.
In applications in the mm wavelength range, bond wires are often used to electrically connect radio-frequency signals from an MMIC (monolithic microwave integrated circuit) to a printed circuit board. Thus, a bond wire is a connective wire connecting the terminals on the chip visible from outside (so-called chip pads) to a substrate. However, in the 77 GHz band for motor vehicle radar applications for example, bond wires are considered as critical both with regard to manufacturing and their electrical characteristics. To obtain reproducible characteristics, very narrow manufacturing tolerances must be kept to. In addition, bond connections of this kind are lossy.
Well-known systems for the mm wavelength range are based on an unbalanced routing on a printed circuit board. The transition to the MMIC is made either by bond wires or by so-called flip-chip mounting of the chip where no wire connections are necessary. However, increased thermal problems arise due to the poorer heat dissipation. Another well-known approach is using so-called “hot vias” which are particularly used in GaAs semiconductor technologies. Here, the chip front side is contacted to the back side using through contactings. The contact to the printed circuit board is made via a patterned back side. This, in turn, entails increased manufacturing costs and the usage thereof is prohibitive in conducting semiconductor substrates (such as, for example, 18.5 ohm cm silicon).
An approach, up to now not realized in motor vehicle radar systems, of integrating mixers into the system is using continually differential architecture in connection with differential antennas. Up to now, integrated circuits based on GaAs technologies have been used. Thus, the lines and transitions from the printed circuit board to a semiconductor chip have mostly been made in an unbalanced manner. With these architectures, bond wires connected to the ground potential conduct radio-frequency signals. This results in undesired interferences in the integrated circuits. In addition, a mode conversion from unbalanced to balanced signal routing within the chip may be necessary, which is a lossy operation.